(a) Field of the Invention
The present invention relates to a plasma display panel (hereinafter, PDP), and more particularly, to a surface discharge type PDP with an electrode structure in which a pair of display electrodes are formed on one substrate and have a corresponding pair of bus electrodes within each discharge cell between two substrates to cause a display discharge.
(b) Description of the Related Art
Generally, a plasma display panel is a display device in which ultraviolet rays generated by gas discharge excite phosphors to realize predetermined images. Such a plasma display panel is popular for wide screen display devices since it enables the manufacture of large screen sizes with high resolution.
Referring to FIG. 8, a generally known PDP is formed with address electrodes 112 along one direction (in the X-axis direction of the drawing) on a rear substrate 110, and a dielectric layer 113 is formed on an entire surface of the rear substrate 110 covering the address electrodes 112. On the dielectric layer 113, barrier ribs 115 of a stripe pattern are formed and placed between each of the address electrodes 112, and red (R), green (G), blue (B) phosphor layers 117 are formed on each of the barrier ribs 115.
In addition, display electrodes 102, 103 having a pair of transparent electrodes 102a, 103a and bus electrodes 102b, 103b are formed along the direction crossing the address electrodes 112 (in the Y-axis direction of the drawing) on a surface of a front substrate 100 opposing the rear substrate 110. A transparent dielectric layer 106 and a MgO protection film 108 are formed covering the display electrodes on a surface of the front substrate 100.
The region where the address electrodes 112 on the rear substrate 110 are intersected with the display electrodes 102, 103 on the front substrate 100 is to be a portion where discharge cells are formed.
An address voltage Va is applied between the address electrodes 112 and the display electrodes 102, 103 to cause address discharge, and a sustain voltage Vs is applied to a pair of the display electrodes 102, 103 to cause sustain discharge. Then, the generated vacuum ultraviolet rays excite phosphors so that they emit visible light through the front substrate 100 and thereby display PDP images.
However, the PDP having the discharge electrodes 102, 103 and the barrier ribs 115 in a stripe formation as shown in FIG. 8, may cause crosstalk between the discharge cells adjacent with the barrier ribs 115. In addition, it may cause the misdischarge between the adjacent discharge cells since the discharge areas are connected to one another along the direction where the barrier ribs 115 are formed. In order to prevent these problems, the distance between the display electrodes 102, 103 corresponding to the adjacent pixels needs to be over a certain level, which reduces improvements in efficiency.
To solve the above problems, PDPs having improved electrodes and barrier ribs as shown in FIG. 9 have been suggested. The PDP has a configuration such that transparent electrodes 123a of display electrodes 123 are extended from bus electrodes 123b to face each other in a pair within each of the discharge cells. For the purpose of reducing the crosstalk between the adjacent discharge cells and enhancing the emission efficiency by increasing the phosphor coated area, a PDP is suggested which has barrier ribs 125 of the matrix type formed with vertical barrier ribs 125a and horizontal barrier ribs 125b perpendicular to each other. Japanese Patent Laid-open No. 1998-149771 describes such a plasma display panel.
A PDP is a display using gas discharge, and its emission efficiency can be varied according to the amount of the excited atoms generated. The emission efficiency is known to increase with increasing total or partial pressure of sealed discharge gases.
If total or partial pressure is increased to improve the efficiency, the breakdown voltage necessarily increases and the discharge instability increases. Sometimes the discharge itself does not take place, and the use of high pressure resistant devices causes an increase in the unit cost of a circuit.
In an effort to lower the breakdown voltage in such a PDP, a gap between discharge electrodes can be decreased when designing discharge electrodes. However, simply decreasing the gap between discharge electrodes may cause several problems.
One problem arising when this gap is decreased is that the discharge path is decreased, thereby deteriorating the emission efficiency of panel. Furthermore, if the gap between discharge electrodes is decreased below a certain value, the breakdown voltage is increased. As shown in the Paschen curve of FIG. 10, if the discharge gas temperature multiplied by the distance between the electrodes (p·d value) becomes lower than a certain value (the minimum value), the Vf voltage value along the Y axis can increase. Accordingly, a decrease in breakdown voltage is needed by properly designing electrodes.
Another problem which can occur when the gap between the discharge electrodes is decreased is related to insulation resistance of dielectric substances. If the gap between the discharge electrodes is decreased, a strong magnetic field is generated between two electrodes and then the possibility of destruction of insulation between the electrodes is increased. It therefore becomes necessary to improve the insulating resistance. Accordingly, these factors must be considered when designing the discharge electrodes.
FIGS. 11a and 11b show a plan view of conventional discharge cells and a light profile graph for sustain discharge in a conventional PDP.
FIG. 11b shows the light emission from the portion within the dotted line in FIG. 11a along the vertical direction (the direction parallel to barrier ribs). Although the bus electrodes supply a voltage, they also have an adverse effect of shielding the visible light generated from a discharge space as shown in FIG. 11b, since the bus electrodes are positioned at the discharge space. Accordingly, this causes the deterioration of the brightness and the emission efficiency.